The Mexican War (1846-1848) was the U.S. Army's first experience waging extended conflict in foreign land. This brief war is often overlooked by casual students of history since it occurred so close to the American Civil War and is overshadowed by the latter's sheer size and scope. Yet, the Mexican War was instrumental in shaping the geographical boundaries of the United States. At the conclusion of this conflict, the U.S. had added some one million square miles of territory, including what today are the states of Texas, Arizona, New Mexico, and California, as well as portions of Colorado, Wyoming, Utah, and Nevada. This newly acquired land also became a battleground between advocates for the expansion of slavery and those who fought to prevent its spread. These sectional and political differences ripped the fabric of the union of states and eventually contributed to the start of the American Civil War, just thirteen years later. In addition, the Mexican War was a proving ground for a generation of U.S. Army leaders who as junior officers in Mexico learned the trade of war and later applied those lessons to the Civil War.

The Mexican War lasted some twenty-six months from its first engagement through the withdrawal of American troops. Fighting took place over thousands of miles, from northern Mexico to Mexico City, and across New Mexico and California. During the conflict, the U.S. Army won a series of decisive conventional battles, all of which highlighted the value of U.S. Military Academy graduates who time and again paved the way for American victories. The Mexican War still has much to teach us about projecting force, conducting operations in hostile territory with a small force that is dwarfed by the local population, urban combat, the difficulties of occupation, and the courage and perseverance of individual soldiers. The following essay is one of eight planned in this series to provide an accessible and readable account of the U.S. Army's role and achievements in the conflict.

This brochure was prepared in the U.S. Army Center of Military History by Stephen A. Carney. I hope that this absorbing account, with its list of further readings, will stimulate further study and reflection. A complete list of the Center of Military History's available works is included on the Center's online catalog.

JOHN S. BROWN
Chief of Military History

Guns Along the Rio Grande
Palo Alto and Resaca de la Palma

The Mexican War was a brief yet significant event in the history of the United States. In eighteen months of fighting, the U.S. Army won a series of decisive victories and captured nearly half of Mexico's territory. In the end, the conflict added some one million square miles of land to the young nation, including the valuable deep-water ports of coastal California.

A period of distrust and misunderstanding preceded the opening of hostilities between the United States and Mexico. After gaining its independence from Spain in 1821, Mexico controlled most of the land north of the Rio Grande that encompasses the present-day states of Texas, New Mexico, Arizona, and California. Between the 1820s and 1840s, English-speaking settlers filtered into this area, which was only marginally controlled by the overextended government in Mexico City. Thousands of Americans, who changed their citizenship and received large tracts of land from the Mexican government, rebelled in Texas in 1835 for several reasons, including Mexico's abolition of the locally popular Texas provincial government and its inability to protect the settlers against Indian raids. These infringements prompted some of the Mexicans living in the region to side with the rebels. Additional causes of the independence movement include cultural differences springing from the Protestant beliefs of the American immigrants and Mexican demands that all become Catholic. Many settlers, moreover, were from the southern states and wanted to introduce slavery into territory that had been free since 1821, an anathema to most Mexicans. The rebels won their independence in 1836 and formed the Republic of Texas. Mexico, however, refused to honor Texas' independence granted by General Antonio Lopez de Santa Anna after the battle of San Jacinto. Consequently, during their years as an independent nation, the Texans did not have formal diplomatic relations with Mexico. Texans insisted that their southern border was the Rio Grande. That claim not only extended the nascent republic's borders some one hundred miles beyond the boundary sought by Mexico, but also added to Texas almost half of the present-day state of New Mexico by virtue of that river's northward turn west of El Paso. Mexico nevertheless continued a Spanish tradition of designating headlands between watercourses as boundaries and claimed that the line ran some hundred miles to the north on heights that separated the Rio Grande and the Nueces River watersheds. The Mexican approach made some sense, as waterways tend to change come over time.

Poor relations between Texas and Mexico intensified in 1844 when Texas applied to become an American state. Mexico declared that it would consider U.S. annexation of the region an act of war. Concerned, President John Tyler directed the U.S. Army to assemble a force called the Army of Observation at Fort Jesup, Louisiana, near the Texas border. After the United States officially annexed Texas on 4 July 1845, the newly elected President James K. Polk ordered the troops to advance into Texas. Polk's decision served as the catalyst for the opening battles of the Mexican War at Palo Alto and Resaca de la Palma in the disputed borderlands.

The United States had interests beyond the Texas issue in Mexico's northern territory. By 1840, the population of the United States had reached approximately thirteen million and was growing rapidly. Looking westward to expand, the nation justified its demand for land with the concept of Manifest Destiny, the notion that God willed the United States to control the entire North American land mass. As expounded by newspaper editor John L. O'Sullivan, the idea became a key part of American ideology in the mid-1840s. Economics also played a central role in the concept. American explorers in California such as 2d Lt. John C. Fremont had reported deepwater ports along the area's coast. These would be valuable when the United States sought to open trade between America's growing industry and lucrative markets in Asia.

In an attempt to settle the Texas border question and secure California, the United States offered to purchase both regions from Mexico several times between 1842 and 1845. Mexico refused all overtures. Mexican popular opinion insisted that the government preserve all of the territory that their nation had wrested from Spain.

Strategic Setting

In 1845 Mexico controlled more than one-third of the North American continent. Its population consisted of nearly seven million people. A geographically diverse land with topographic extremes, its highest point soared to 18,700 feet above sea level while its lowest stood below sea level. Coastal plains dominated much of eastern Mexico, but the terrain rapidly inclined into a region of central plateaus and interior mountains. The nation's largest population center, Mexico City, was situated in a volcanic highland region in the center of the country.

Northern Mexico, where most military operations occurred in 1846, shared many of these characteristics. The Gulf area consisted of coastal flats, while wide flood plains encompassed both banks of the Rio Grande. The topography ascended southward into stretches of arid lowlands, which gradually gave way to cool highlands. The Sierra Madre towered over most

of the region. North of the Rio Grande, Mexico's holdings extended from the western borders of the states of Louisiana and Arkansas in the east to the Pacific Ocean in the west. They included more than one million square miles of land in the present-day states of Colorado, Wyoming, Utah, Nevada, New Mexico, Arizona, and California. The geography of this sparsely populated territory included parts of the jagged Rocky Mountains and the Sierra Nevada, the craggy Intermountain Region, and the rugged Coast Ranges. In addition, stretches of largely uninhabited desert contrasted with such potentially valuable agricultural lands as California's Central Valley.

As with the terrain, Mexico's climate presented huge variations, ranging from oppressive humidity in heavily jungle, tropical regions on the coasts to extreme winter conditions in the interior mountains. Much of the plateau region was desert land that suffered from prolonged droughts.

On the brink of conflict, Mexico appeared better prepared for war than the United States. Its Army numbered 18,882 regular troops, 10,495 active militiamen, and 1,174 irregulars. In comparison, the U. S. Army's authorized strength was 8,613 and its actual establishment only 7,365.

Both the American and Mexican armies shared a similar organization based on European models, with specialized corps

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of infantry, cavalry, artillery, and engineers. Organized to guard the frontier and to fight small unit actions against American Indians, the U.S. Army of the 1840s was scattered across America's coastal regions and frontier in small posts manned by units of company size or less. Because entire regiments rarely assembled, the force hardly ever practiced large unit tactics. The Mexican army was little different. It had five territorial divisions, each of which covered a different geographical region out of necessity. That organization required the deployment of small detachments across huge areas. Few of those units had ever served with others in their divisions. Thus neither side had much experience with conventional warfare involving larger units of different arms.

The U.S. infantry consisted of eight regiments, each containing ten companies. Each company supposedly possessed fifty-five men, but at the onset of the war most were understrength, averaging only thirty-five. Battalions, along with brigades and divisions, were employed frequently during the Mexican War. A battalion denoted an ad hoc collection of companies that assembled to perform a special task during a campaign and then dissolved when the mission was over. Brigades consisted of multiple regiments, while divisions contained several brigades. These larger formations were also temporary organizations.

The standard American infantry weapon was the 1835 model smoothbore flintlock musket. Inaccurate at best, the musket had an approximate target-hit ratio of 10 percent at one hundred yards. Percussion cap muskets and rifled weapons accurate to distances of five hundred yards were available, but both saw only limited service in the war and did not become standard issue until after the conflict. Drill conformed to Maj. Gen. Winfield Scott's Infantry Tactics manual, revised in 1840, which stressed close-order formations, maneuver, and light infantry or skirmish line tactics.

The Mexican army maintained twelve permanent infantry regiments, each divided into two battalions of eight companies with eighty men per company. In reality these manpower levels were never maintained. Mexican soldiers were poorly armed with out-of-date, inaccurate, and often unserviceable muzzleloading flintlock muskets. Drill thus emphasized precision marching but did not incorporate target practice to reduce wear and tear on the force's limited inventory of antiquated weapons.

Infantrymen in the American army enlisted for five years and received an average pay of $7 per month. Offering low wages and harsh discipline, the service attracted the poorly educated and those with few opportunities in civilian life. In 1845 the army included 42 percent foreign nationals, of which 50 percent were Irish. The rest came from

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Germany, Italy, England, France, and other European nations. By contrast, the Mexican infantry was made up of conscripts who served for six years. Most were Indians or mestizos, individuals of mixed European and Indian ancestry.

America's mounted forces were called dragoons and classified as light cavalry. The Regular Army had two cavalry regiments, both organized into five squadrons, each containing two companies. The primary weapons employed were the 1840 model cavalry sabre, a single-shot pistol, and an 1843 model breechloading carbine for use while dismounted.

Deeply revered because Mexico's people held horsemen in the highest esteem, Mexico's cavalry was organized into nine regiments, each containing four squadrons made up of two companies. Their troopers carried a variety of weapons, including sabres, pistols, carbines, escopetas (a blunderbuss-type shotgun), lassos, and lances. The nine-foot-long lance was a particularly efficient weapon in close combat, especially in the hands of well-trained lancers, who were also excellent horsemen.

American light field artillery batteries were supposed to have three 2-gun sections. Because of manpower shortages, however, most could only mount four guns at the onset of the Mexican War. The primary field piece was the bronze 6-pounder, which weighed 880 pounds and was accurate to fifteen hundred yards. Twelve-pound pieces weighing 1,800 pounds were also sometimes employed. Each light battery came with a large number of horses to transport the guns, ammunition, and most of its crew. As a result, the artillery was highly mobile and able to respond to tactical threats over what were great distances by the standards of the 1840s. The U.S. Army also used 18- and 24-pound pieces, heavy guns designed primarily for sieges and coastal defense. Unlike the 6-pounders, they were drawn by teams of eight oxen and moved slowly. While cumbersome, they nonetheless provided massive firepower. Because the larger guns were difficult to transport, the U.S. Army often employed artillerymen assigned to costal defense batteries as light infantry.

In theory, the Mexican artillery deployed at a ratio of four guns for every one thousand soldiers. In reality, brigades usually possessed few guns of mixed types and calibers: 2-, 4-, 6-, 8-, 12-, and 16-pound guns cast from iron and bronze. As a result, Mexican artillery lacked sufficient logistical support and was generally ineffective on the battlefield. The guns were often quite old, mostly forged in the 1770s. Because of their age and design, they were heavy, difficult to maneuver, slow to reload, and grossly inaccurate. In addition, many were defective and dangerous to fire.

The U.S. Army employed a small number of highly trained engineers who served in either the Corps of Engineers or the Corps of

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Topographical Engineers. Members of the former specialized in bridge and fortification construction. Topographical engineers created maps, surveyed battlefield terrain, and built such civil engineering projects as roads and canals. In contrast, the Mexican Engineer Corps was organized into Zapadore or Sapper battalions that combined both of the American specialties.

Three departments--Quartermaster, Ordnance, and Subsistence-provided logistical support for the U.S. Army. The Quartermaster Department, the most important of the three, supplied troops with all equipment other than weapons: uniforms, horses, saddles, tents, and food. It also arranged transportation, oversaw construction projects, and, during the Mexican War, created and ran a series of advanced supply depots close to field operating forces that ensured a steady flow of provisions and equipment to the troops. Although its long supply lines sometimes became targets for Mexican irregulars and bandits, the Quartermaster Department provided the U.S. Army with one of the most advanced logistical support operations in the world. The Ordnance Department supplied firearms and ammunition, while the Subsistence Department secured bulk items, such as barrels of flour, salt pork, and cured beef; both departments operated in the rear along the Army's lines of communication.

In contrast, the Mexican army lacked dedicated supply bureaus and employed administrative arrangements common in European armies of the preceding century. Under this system, the war ministry provided funds to regimental commanders to purchase supplies and equipment for their men. The regimental commanders in turn distributed the money to company commanders who made the actual purchases with little accountability. The system was inefficient and burdensome to the tactical commander. These arrangements also allowed underpaid, less than conscientious officers responsible for purchasing supplies to embezzle large sums for their own use. Such practices forced troops to forage for supplies and hampered their ability to march cross-country with any speed. They were also often short on ammunition and gunpowder.

Although Mexico's army was larger than that of its U.S. enemy, its fighting ability was hampered by low morale; poor training; a high number of conscripts; and an unusually high ratio of officers to enlisted personnel, often one general for every two hundred men. Many of the officers were poorly trained and held their positions because of wealth or political allegiances.

The U.S. force, for its part, had several advantages that compensated for its small size. United States Military Academy graduates trained in the art and science of war occupied many midlevel and junior command positions and would play key roles in the combat operations. If the senior

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commanders of the Regular Amy-Winfield Scott, Zachary Taylor, Stephen W. Kearny, and John E. Wool-lacked formal military education, they nonetheless had learned the art of war during the War of 1812 and in numerous campaigns against American Indians. Scott, in particular, had studied widely the professional literature, largely of European origin, to educate himself.

The Army of Observation that President Tyler established was commanded by Bvt. Brig. Gen. Zachary Taylor, known to his troops as Old Rough and Ready for his casual demeanor, strict discipline, and stubbornness in battle. Although Taylor had served in the army since the War of 1812, promotions in the peacetime army of the period were extremely slow, so he held only a brevet, or honorary rank that gave him the title and authority of a brigadier general but none of the pay and benefits. The force General Taylor was to command numbered 1,200 men, roughly 15 percent of the Regular Army. As tensions mounted in May 1845, however, Secretary of War William L. Marcy augmented it with nearly 2,000 troops and prepared to send it to Texas. When the Texas Congress voted to join the United States on 4 July 1845, newly elected President James K. Polk ordered the force into Texas. Renamed the Army of Occupation by Taylor, it camped on the edge of the disputed territory at Corpus Christi, located at the point where the Nueces River flowed into the Gulf of Mexico.

Growing to 3,554 men, about half of the Regular Army's strength, the Army of Occupation spent seven months on the plains of Corpus Christi. The weather was pleasant during the late summer, but the cold, wet winter that soon set in made life difficult for the troops. Even so, the men spent up to eight hours a day during much of their encampment practicing regimental and brigade maneuvers, marksmanship, and bayonet techniques, and conducting parades, reviews, and other necessary drills. Those efforts honed the ability of both officers and troops to mount large-scale operations. Large unit tactics were a skill not much practiced since the War of 1812, even though Winfield Scott had established brigade-size camps of instruction in the 1830s, and the army had employed brigades during the Black Hawk and Second Seminole Wars. The training would prove invaluable during the initial battles of the war.

After a final attempt to pressure Mexico to settle on a boundary for Texas and to sell California, Secretary of War Marcy ordered General Taylor to move his army to the Rio Grande on 8 March 1846. Taylor's destination was on the river's north bank, directly opposite the Mexican town of Matamoros, which stood at a natural choke point on the river and controlled access to well-traveled routes to the south. The Army of Occupation began constructing an earthen fortification called Fort Texas, the present-day site of Brownsville. Point Isabel at the mouth of the Rio Grande served

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General Taylor (National Portrait Gallery, Smithsonian Institution)

as Taylor's supply depot. Supplies came by ship across the Gulf of Mexico to an offshore island, moved by ferry to Point Isabel, and then went overland to Fort Texas, twenty miles to the west.

General Mariano Arista commanded Mexico's Army of the North defending Matamoros. Responsible for guarding the Texas frontier, his force was the best trained and motivated in the Mexican army. Arista considered Taylor's arrival on the Rio Grande an act of aggression and demanded that the Army of Occupation withdraw north of the Nueces

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Taylor's camp along the beach in Corpus Christi. The wide and open fields behind the American encampment were crucial for drilling troops and teaching large unit formations. (Library of Congress)

River. At the same time, Mexican authorities made numerous attempts to entice American Catholic soldiers to join their side, but fewer than one hundred deserted.

When Taylor refused to leave the region, Mexican cavalry ambushed a dragoon detachment under Capt. Seth B. Thornton on 25 April 1846. American losses were 11 dead, 6 wounded, and 46 captured. Although there had been earlier skirmishes with Mexican irregulars, the Thornton skirmish became the official start of hostilities. News of the engagement reached President Polk on 9 May 1846. Two days later a declaration of war message was sent to Congress. By then Taylor had fought and won the first two battles of the conflict. This delay was due to the lack of any effective communication channels: The War Department only had access to telegraph lines that ran between Washington, D.C., and the quartermaster depot in Philadelphia. All communiqués from the theater of operations had to come by messenger or by ship, a process that greatly slowed the flow of news.

General Arista planned to cross the Rio Grande downriver from Fort Texas and sever Taylor's supply line. Taylor, however, received intelligence of Arista's actions and hurriedly assembled a 2,300-man relief force to secure his supplies at Point Isabel. He left 500 men under Maj. Jacob Brown to guard Fort Texas. Departing on 1 May

1846, Taylor's force reached Point Isabel before Arista could cut the route to the depot. Once there, it began to load 270 wagons with supplies for Fort Texas.

Unable to prevent Taylor's move, General Arista decided to destroy Fort Texas and its defenders before the American force at Point Isabel could return. Crossing the Rio Grande on 3 May, the general divided his army into two columns. One under his own command blocked the road between Point Isabel and Matamoros to bar Taylor's return to Fort Texas. The other column moved on Fort Texas, where it began a heavy bombardment that lasted over five days. The defenders withstood everything the Mexicans could throw at them, but their commander, Major Brown, died at his post.

Taylor's force at Point Isabel could hear the cannonade against Fort Texas and hurried to complete its mission. With the depot's defenses

well in order and his wagons loaded, Taylor's column began a slow march back to Fort Texas on the afternoon of 7 May. The force traveled only seven miles before bivouacking for the night. When Mexican scouts found it the next morning, General Arista ordered his men to take up position on a broad plain at Palo Alto, eight miles northeast of Ft. Texas on the Point Isabel-Matamoros road. Palo Alto, "Tall Timber," was a two-mile-wide flat prairie with several small ponds located on its perimeter. The center of the plain was marshy owing to several days of heavy rain. The area was covered with sharp, shoulder-high grass, and sections were lightly wooded with mesquite trees that extended southward toward the Rio Grande.

Operations

Palo Alto, 8 May 1846

General Arista stationed 3,702 men on the south side of the field and faced due north, forming a line that stretched from the road eastward to a tree-covered rise. His flanks were protected by dense chaparral-short, thorny underbrush-that limited movement. He hid part

of his irregular cavalry to the far left of his line in an attempt to quash any chance that the Americans could flank his position from that direction. When he was done, the only way Taylor could reach Fort Texas was through the Mexican Army of the North.

American scouts located Arista's line shortly before noon. While Taylor's 2,228 men concentrated at a large lake on the north side of the prairie called Palo Alto Pond, Lt. Jacob E. Blake, a topographical engineer, conducted a reconnaissance of the Mexican position. He observed that the Mexican line was approximately one mile

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long. On their far left, General Antonio Canales' irregular cavalry was positioned in the chaparral to the west of the Point Isabel road. Blocking the road and holding the center of the line were a brigade of cavalry under the command of Brig. Gen. Anastasio Torrejon and several infantry brigades led by General Jose Maria Garcia. The infantry units contained Garcia's 4th and 10th Infantry regiments and General Romulo Diaz de la Vega's 6th and 1st Infantry regiments. On the right stood the Tampico Corps, the 2d Light Infantry regiment, and a sapper battalion. Light cavalry anchored the extreme eastern end of the line, holding against a tree-covered rise. Two 8- and six 4-pound artillery pieces were dispersed along the Mexican front.

Facing due south, General Taylor concentrated his troops across a half-mile expanse. He divided his force into two wings under Col. David E. Twiggs and Lt. Col. William Belknap. Twiggs controlled the units on the right wing, with Lt. Col. James S. McIntosh's 5th Infantry regiment and a battery of 6-pounders under Bvt. Maj. Samuel Ringgold anchoring the position's extreme right or western flank. They were positioned just beyond the Point Isabel-Matamoros road. Two 18- pounders commanded by Lt. William H. Churchill and the 3d Infantry regiment led by Capt. Lewis N. Morris held the road itself. Capt.. George W. Allen's 4th Infantry regiment guarded Morris' left. Capt. Charles A. May's squadron of dragoons held to the rear in reserve.

Belknap commanded the left wing, which included a battalion of artillerymen fighting as infantry under Lt. Col. Thomas Childs, who held the center of the American position and was stationed to Captain Allen's left. They were known as red-legged infantry because the legs of artillery uniforms always bore red stripes. Captain William Duncan's battery of 6-pounders supported them. The 8th Infantry regiment under Capt. William Montgomery held the extreme left or eastern flank. It refused its left to the rear at a ninety-degree angle to keep the enemy from flanking the American position. Captain Croghan Ker's squadron of dragoons screened the left flank and protected Taylor's supply train, which was parked on a levee for the Palo Alto Pond.

The engagement commenced at 1430 when the Mexican artillery opened fire on the deploying Americans at a range of one-half mile. In response, Major Ringgold and Captain Duncan pushed their batteries two hundred yards ahead of Taylor's line and initiated counterbattery fire. From the onset, it was clear that the US. artillery would dominate on the open field of battle, if only because the Mexicans' copper cannons lacked the necessary range to be effective. Their iron round shot often fell short of their targets and bounced slowly toward Taylor's men. By contrast, the American guns were updated 1840 model weapons with

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First phase of the Battle of Palo Alto. The US. infantrymen are standing in ranks as the American artillery wreak havoc on the Mexican lines. (Library of Congress)

a range of fifteen hundred yards and could be reloaded quickly. Moreover, their advanced design allowed cannoneers to vary their ammunition depending on tactical circumstances. The guns primarily used solid shot or spherical case loaded with metal shards that exploded in midair and spread fragments over a large area. Most important, the U.S. artillerists were well trained in techniques designed by Major Ringgold and practiced at the Artillery School located at Fortress Monroe, Virginia; their fire would prove highly accurate.

As a result of this preparation, the American artillery decimated the Mexican infantry, time and again hitting specific targets in the ranks. In one instance, a gunner in Ringgold's battery used a single explosive shell to lay waste an entire regimental band playing to rally the troops. Lieutenant Churchill's cumbersome 18-pounders soon joined the cannonade. He and Ringgold concentrated their firepower on the Mexican's left, while Captain Duncan continued his counterbattery fire.

In an attempt to allay the effect of the American artillery, General Arista ordered a western flanking maneuver to turn Taylor's right wing and destroy his supply train. Torrejon's cavalry, supported by two 4-pound guns, closed within fifty yards of the American's right through the thick chaparral. Observing the Mexican advance, Taylor warned Twiggs, who ordered

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Major Ringgold (National Portrait Gallery, Smithsonian Institution)

the 5th Infantry regiment into a square formation and directed 1st Lt. Randolph Ridgely to rush his two-gun section to the area. When Torrejon's force emerged from the chaparral and charged the west side of the square, concentrated musket and 6-pound artillery fire forced it to pull back. The Mexicans regrouped and attempted to swing further west around the 5th Infantry's arc of fire to strike the American wagons, but blundered into range of the 3d Infantry. Deployed in a square, the force poured lire into the attacking cavalry. In the end, Torrejon retreated to the Mexican line with heavy casualties. The Americans

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Contemporary depiction of the death of Major Ringgold (Library of Congress)

lost no more than a few wounded. For the moment, the American supplies were safe.

As the U.S. forces asserted control, Major Ringgold moved his guns farther forward and continued to target the Mexican infantry. The onslaught halted only at 1600, when a fire caused by burning paper wads from the guns ignited the prairie grass and obscured the battlefield. During the pause, officers allowed men overwhelmed by the heat of the day and the blazing fire to fall out of line and refill their canteens at a nearby pond.

After a lull of about an hour, Taylor adjusted his line, advancing his 18- pounders approximately one thousand yards forward on the right side up the Camino de los Indios and pulling his left wing back to maintain a continuous and unbroken line of battle. General Arista responded by moving his left flank to the rear while pushing units on the right forward some four hundred yards. In effect, the two sides had rotated the battle's orientation counterclockwise by approximately thirty-five degrees while maintaining the one-half mile separation between their main lines.

At 1700 the fighting renewed. General Arista began the contest aggressively by ordering Torrejon's cavalry to make another assault on the American's right. Fire from Churchill's 18-pounders and several volleys from Colonel Child's artillery battalion, which had formed a defen-

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Duncan's battery stemming the final Mexican thrust during the Battle of Palo Alto. (University of Texas at Arlington)

sive square, beats back the advance. Arista then ordered his artillery to concentrate on Ringgold's battery, which had closed to within four hundred yards of the Mexican line and was, therefore, within effective range of the Mexican cannons. The heavy fire that followed mortally wounded Ringgold and forced the American guns to pull back.

In a final attempt to destroy Taylor's supplies, Arista tried to turn the American left or eastern flank with a force of light cavalry supported by his 2d Light Infantry regiment. Obscured by smoke from the still smoldering grass, the Mexican force seemed to have an unimpeded path around the 8th Infantry to the American wagon train. Captain Duncan, however, saw the enemy emerging from the dense chaparral. Racing his battery to the front of the flanking force, he poured canister shot (a large number of small-caliber metal balls loaded into a metal container that produced a shot-gun effect when fired) directly into its center and right flank. The 8th Infantry and Captain Ker's dragoons moved forward as well to provide additional support. With their advance checked and suffering heavy causalities, the Mexicans retreated. Duncan pushed his battery forward in pursuit and unlimbered again less than three hundred yards from the Mexican right flank. After hours of being pounded by the American artillery, the

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Mexican line began to falter. When a force of light cavalry retreated across the front of the Mexican position, it caused a general panic, but units at the Mexican center nonetheless held firm, stabilizing Arista's line and preventing a rout.

By 1900 the Mexicans had nearly exhausted their supplies. With darkness falling, Arista's battered troops withdrew to the rear of the battlefield and camped for the night. At that point, Taylor decided against ordering a night assault to finish the Mexican army. Another encounter would thus be necessary to do the job. In all, the Mexican force had lost about four hundred men dead and an undetermined number of wounded and missing. United States losses came to six dead and forty wounded. Overall, the engagement represented a tremendous tactical victory for America's Regular Army.

Resaca de la Palma (9 May 1846)

Shortly before dawn on 9 May, General Arista decided against engaging Taylor again at Palo Alto primarily because of the effectiveness of U.S. artillery on open ground. Searching for more favorable terrain, the Mexican commander led his army some five miles south to Resaca de la Palma, a place dominated by rolling hills covered with a thick tangle of trees and chaparral that greatly hindered visibility and mobility. There, a resaca, or dry riverbed, cut a two-mile-long, two-hundred-yard-wide, twelve-foot-deep furrow across the area. Both banks of the cut were heavily forested. The troops pitched camp in an open field at a point where the resaca crossed the Point Isabel-Matamoros road. Areas of wet swampy ground also protected the Mexican line. Arista and his staff had chosen a defensive position well calculated to minimize the effectiveness of the American artillery.

Arista ordered the troops besieging Fort Texas to join his command at Resaca de la Palma. This concentration of forces gave him about 3,600 men. Meanwhile, Taylor remained unaware of Arista's movement until his scouts observed the rear guard of the Mexican army departing Palo Alto shortly after daybreak. Calling his senior officers to a council of war to debate options, Taylor decided to construct an earthwork at Palo Alto Pond to protect his supply wagons and then to move his force forward to locate and destroy the Mexicans. Captain Ker's dragoons shadowed the enemy force to Resaca de la Palma. Taylor sent a light battalion of the 4th Infantry under the command of Capt. George A. McCall to reconnoiter the position.

At approximately 1400 Taylor ordered Ringgold's battery, now commanded by Lieutenant Ridgely, to move down the Point Isabel-

Matamoros road. The 34 4th, 5th, and 8th Infantry regiments and May's squadron of dragoons followed. In all, Taylor had 1,800 men to fight at Resaca de la Palma. He divided them into two brigades: the lst, composed of the 4th and 8th Infantry under Colonel Belknap, and the 2d, made up of the 3d and 5th Infantry and the dragoons commanded by Twiggs. This left nearly 500 men-Churchill's two 18-pound guns, Duncan's bat-

As General Taylor began his march from Palo Alto, 1st Lt. Stephen D. Dobbins and several volunteers under Captain McCall's command deliberately exposed themselves to draw enemy fire and pinpoint Mexican positions. They found that Arista had arrayed the bulk of his infantry on the north bank of the resaca. On the Mexican right or eastern flank, straddling the Matamoros road, stood the 6th, 10th, and 1st Infantry regiments along with a sapper battalion and the 2d Light Infantry. On the left were the 2d and 4th Infantry regiments and the Tampico Battalion. Arista's artillery pieces covered the resaca and the Matamoros road to prevent an American breakthrough. Skirmishers were in position several hundred feet to the front to screen the Mexican line. Several light and heavy cavalry regiments meanwhile held in reserve just south of the resaca.

With Captain McCall's battalion advancing in a skirmish line to provide support, General Taylor sent Lieutenant Ridgely's guns forward on the Matamoros road. As additional regiments came up, Taylor deployed them piecemeal into the chaparral to follow McCall's skirmishers. The 3d Infantry deployed to the west of the road on the extreme right. The 4th

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Infantry straddled it, and the 5th Infantry occupied the extreme left to its east. The 8th Infantry initially stood in reserve. As these forces moved into place, Taylor planned to use the light artillery to locate weaknesses in the Mexican line that May's dragoons and the infantry could exploit.

Shortly after Ridgely pushed forward, McCall's troops became scattered in the heavy chaparral and lost contact with the artillery. Meanwhile, the rest of the American force came under heavy fire from the Mexican skirmish line hidden in the underbrush. McCall struggled to organize his men for an attack to relieve the pressure, but found a concerted advance impossible because of the difficult terrain. Instead, his men broke into small groups to navigate through the chaparral, each led by a lieutenant or a noncommissioned officer. There was no coordination between the various squads as they moved forward, but after some sharp fighting, these units successfully drove the Mexican skirmishers to the edge of the resaca. They could not, however, make any headway against Arista's main line, which was firmly positioned on the forested edges of the ravine.

Arista tried to pave the way for an attack of his own by sending a detachment of cavalry out of reserve to eliminate Ridgley's battery. With his infantry support out of contact, the redoubtable lieutenant beat back the Mexican advance with canister. After stemming the assault, however, he came under heavy fire from a Mexican battery and requested aid from Taylor.

In response, Taylor ordered May's dragoons to capture the battery. Ridgely exchanged a volley with it, and May's men charged forward before the Mexicans could reload their cannons. The momentum of the thrust, however, carried the dragoons beyond the guns and exposed them to heavy fire from the Mexican infantry lining the bank of the resaca. Facing annihilation, the force retreated hastily, forfeiting its chance to capture the battery. Even so, it did manage to capture one of Arista's commanders, Brig. Gen. Romulo Diaz de la Vega.

Realizing that a full-scale infantry assault was necessary if he was going to make any headway, Taylor ordered the 5th Infantry forward and brought the 8th Infantry out of reserve. As before, the two units found it difficult to advance through the tangled underbrush in line formation, ultimately breaking into small groups. Nevertheless, rushing forward as best they could, they took the Mexicans on in bloody hand-to-hand combat with bayonets and rifle butts, capturing the guns. The Mexican's right quickly collapsed after that, but the Americans' success came at a price, eight dead and thirty-five wounded.

While the battle raged on the enemy's right, several companies of the 4th Infantry commanded by Capt. Robert C. Buchanan found a small trail on the western flank that circumvented the Mexican's left. General Arista

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observed the American force flanking his position and rushed reinforcements into the area, but a company under Capt. Philip Nathan Barbour nonetheless drove through the Mexican line, crossed the resaca, captured an artillery piece, and turned the Mexican's left. Arista counterattacked the small American contingent twice but failed to dislodge it. With the Mexican infantry physically and emotionally exhausted, the failure of these counterattacks caused the entire Mexican line to disintegrate and flee from the field in an all-out rout. Surprised by the sudden collapse of his army, Arista abandoned his headquarters, leaving all his personal possessions behind. Taylor attempted to finish the Mexican force by sending Captain Ker's dragoons, a battery from Palo Alto, and the 3d Infantry in pursuit, but they were unable to catch the rapidly retreating Mexicans.

Involving a force that had been outnumbered two to one by an enemy who held a strong defensive position, General Taylor's victory at Resaca de la Palma was decisive; but it was more costly than the one at Palo Alto, which was won mainly by the artillery. Out of the 1,800 Americans engaged on 9 May, Taylor lost 45 killed and 98 wounded, most in vicious hand-to-hand combat. Official Mexican casualties were 154 killed, 205 wounded, and 156 missing. Many of the missing men most likely drowned while attempting to swim the Rio Grande to escape the pursuing Americans. Besides General de la Vega, Taylor's men captured a number of Mexican soldiers during the two battles. They were repatriated on 10 May 1846 in exchange for the 46 Americans captured in the Thornton ambush.

Analysis

With the victory at Resaca de la Palma, General Taylor accomplished much. He relieved his besieged troops at Fort Texas-soon renamed Fort Brown in honor of the post's original commander who had died during the siege-and drove the Mexicans south of the Rio Grande. Taylor thus succeeded in securing the southern border that the United States claimed. His victories would pave the way for an invasion of northern Mexico that began on 18 May 1846, when American forces crossed the Rio Grande and occupied Matamoros unopposed. In addition, the president promptly promoted Taylor to major general on 29 June 1846, the &st step in his meteoric rise to the presidency two years later. His triumphs made him a national hero and his name a household word.

The opening battles of the Mexican War were also important for the U.S. Army. The battle of New Orleans, the last major engagement on land during the War of 1812, had elevated the militia to a near iconic status in

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American popular culture. Palo Alto and Resaca de la Palma did something similar for the Regular Army. The opening campaigns of the Mexican War validated the importance of maintaining a professional, standing army. Before the Mexican War, many Americans had argued against funding a regular army and had instead placed their trust in volunteer forces made up of citizen-soldiers. At Palo Alto and Resaca de la Palma, however, the Army of Occupation consisted entirely of professional soldiers and had proved its mettle on the battlefield. The victories in these two engagements against an enemy with a significant numerical advantage demonstrated the benefits derived from a trained and ready force available at the onset of a conflict, something the United States had never enjoyed in the past and would all too often fail to benefit from in the future. In the opening days of the Mexican War, however, the American Regular Army was able to leverage advantages of training, equipment, organization, and leadership into stunning battlefield victories.

The two battles also proved that American artillery was as advanced as any in the world. Largely through the efforts of Joel R. Poinsett, while he was the secretary of war from 1837 to 1841, and Major Ringgold, the creation of light and mobile field artillery had given the United States Army a potent weapon. More importantly, the artillerists trained by Ringgold had proved to American officers that artillery was not only a defensive weapon but also, if used correctly, an effective offensive force that could dominate a battlefield from an advanced position. These lessons affected the tactics of the U.S. Army throughout the Mexican War and later.

In a wider historical perspective, these battles were early instances in which the U.S. Army enjoyed technological superiority over a conventional foe. The result was victory with marked savings in American lives. This circumstance, little noted at the time, was in fact the first harbinger of what would become a dominant theme in American military experience during the second half of the twentieth century.

The engagements in southern Texas also validated the quality of the education provided by the United States Military Academy at West Point. Because of slow promotions, low pay, and lack of a pension system, field-grade officers often held their commands until death. As a result, many American senior officers were too old or too sick to command their regiments on the Rio Grande. It was their junior officers-younger, desperate for brevets and mostly trained at the academy-who led the fights at Palo Alto and Resaca de la Palma. Their training and education were a major reason that those engagements ended in victory for the U.S. Army.

The battle at Resaca de la Palma likewise highlighted the quality of the Army's noncommissioned officers. With large unit movements impossible and visual communication hampered by dense chaparral,

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sergeants and corporals led groups of soldiers against hasty Mexican field fortifications. It was largely through their uncoordinated but determined efforts that Taylor's army was able to drive Arista's force south of the Rio Grande.

Mexico's losses at Palo Alto and Resaca de la Palma had major repercussions for its armed forces. General Arista was court-martialed for his failure to defend the northern border and replaced by General Pedro de Ampudia, a cruel but capable leader. Ampudia decided to withdraw his command to the south to force Taylor to extend his lines of communication by carrying the fight into the heart of northern Mexico. Arista's inability to keep American forces from advancing also paved the way for Antonio Lopez de Santa Anna's return to Mexico from exile in Cuba in August 1846. Subsequently, Santa Anna ascended to the presidency and would personally lead the main Mexican Army through the rest of the conflict.

Traas, Adrain G. From the Golden Gate to Mexico City: The U.S. Army Topographical Engineers in the Mexican.....War, 1846-1848. Washington, D.C.: Corps of Engineers and U.S. Army Center of Military History, 1993.

Winders, Richard B. Mr. Polk's Army: The American Military Experience in the Mexican War. College Station, Tex.: .....Texas A&M University Press, 1997.